Analysis of Frequency Domain Electromagnetic Response Characteristic in Inhomogeneous Medium

Frequency domain electromagnetic method is a way to study the Earth's electrical structure by use of an alternating electromagnetic field. According to the basic theory of the electromagnetic field, the general expressions of frequency domain electromagnetic response are derived. Which are applied to the infinite homogeneous medium and horizontal inhomogeneous medium, respectively. The response characteristics of different formation conductivity show that the formation conductivity has a significant impact on the choices of transmitted signal frequency. In order to achieve the inhomogeneous medium detection, the transmission frequency should be within the range of lower frequency. The numerical results of frequency responses for different intermediate layer thickness indicate when the formation conductivity remains unchanged, the higher the intermediate layer thickness, the more the response amplitude. However, the transmit frequency corresponding to response signal peak is not removed.